Which nutrient is most important for energy in livestock diets?

Carbohydrates are the most important nutrient for energy in livestock diets because they serve as a primary energy source that animals can readily digest and utilize. Carbohydrates are composed of sugars and starches, which are easily broken down into glucose, the main energy molecule used by the body's cells. This energy is crucial for day-to-day bodily functions, growth, reproduction, and overall health in livestock.

While fats are also a significant energy source and provide more energy per gram than carbohydrates, they are not used as the primary energy source in most animal diets, especially for livestock. Proteins, on the other hand, are primarily used for growth, repair, and maintenance of body tissues, rather than for energy. Vitamins, while essential for various metabolic functions, do not provide energy directly. Thus, carbohydrates are essential for meeting the energy demands of livestock, making them the correct answer.